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Mackie Onyx 400F
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Mackie Onyx 400F

Interface audio FireWire de la marque Mackie appartenant à la série Onyx

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Sujet Infos rapport S/B .

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Sujet de la discussion Infos rapport S/B .
Heu, une petite question.... Sur le site de MACKIE, il est annoncé un rapport signal/bruit de 87 db ...

" Signal-to-Noise:
>87 dB (ref. +4 dBu, Mic In to Line Out, Gain @ unity)
Equivalent Input Noise (E.I.N.), 20 Hz to 20 kHz Bandwidth, 150Ω source impedance:
–129 dBu @ +60 dB gain "

C'est digne d'un magnéto cassette ça, non ????
Ou est l'erreur... :???:
2
En effet c'est un peu faible. Pour comparer une petite Soundblaster Audigy (c'est pas bon je sais) arrive à un rapport signal/noise de 100 db et la fireface 800 RME atteint les 119 db.

J'ai un pote qui était parti pour acheter la Onyx 400f et heureusement tu as fait cette remarque: maintenant il hésite fortement. En effet "supérieur à 87 db" cela ne veut pas dire grand chose.
Old songs, stay till the end. Sad songs, remind me of friends. And the way it is, I could leave it all, And I ask myself, would you care at all.
3
J'ai posé la question sur le forum de mackie et voici ce que l'on m'a repondu. C'est un peu compliqué (et en anglais en plus) mais en gros je crois que ce qu'il faut retenir c'est que les chiffres indiqués dependent de la façon dont il ont été mesurés et donc qu'il ne faut pas comparer 2 chiffres pour des cartes concurrentes sous pretexte qu'il y a les mots signal et noise... ca veut tout et rien dire et c'est souvent du marketing...
L'onyx est qd meme largement meilleure qu'une sound blaster faut pas deconner ;-)

Voici la reponse en anglais:

quote:
--------------------------------------------------------------------------------
Originally posted by Mikk25:
" Signal-to-Noise:
>87 dB (ref. +4 dBu, Mic In to Line Out, Gain @ unity)
Equivalent Input Noise (E.I.N.), 20 Hz to 20 kHz Bandwidth, 150Ω source impedance:
–129 dBu @ +60 dB gain "

I'am not sure to understand the 87db... Is it the SNR that can be compared to the more than 100db SNR for the Fireface?
--------------------------------------------------------------------------------

You can't compare anything to anything unless you know how each one makes their measurements. Mackie is pretty good about this, at least for their newest products.

Acutally, those two specifications say the same thing. Here's how:

EIN (Equivalent Input Noise) is the noise present at the output with no signal at the input, and with the amount of gain subtracted out. So this means that with no input signal and maximum (60 dB) gain, there will be -69 dBu (129 - 60) of noise coming out.

Signal-to-noise ratio is the ratio of the maximum output level to the noise level with no input. -87 dBu is the noise referenced to +4 dBu. The maximum output level is +22 dBu (I'm guessing at this to make the numbers come out right, but it's probably correct). That's 18 dB higher than +4 dBu. -87 dBu referenced to +4 dBu + 18 dBu (headroom over +4 dBu) = -69 dBu

Confused yet? Good. That's the way they like it. Incidentally, EIN is really more of a designer's parameter than a product specification, but marketing departments really love it because it's a really small number that has "noise" assoicated with it, and that's gotta be a good thing, eh? At leat Mackie specifies the "dummy microphone" (150 ohms) that they're using for the measurements. The type of transistors (BJT) that are used in the front end of most mic preamps generate some current noise which doesn't appear in noise measurements if you use a shorted input, but is a real world contributor to output noise when connected to a real microphone.

With a shorted input (which is the obvious way to test, and a few people think this should be the standard procuedure for measuring preamp noise), the noise spec looks about 3 dB better than with a 150 ohm input termination (which other people think should be the standard way of measuring preamp noise). You won't see that noise improvement in the real world, however, since typical mics look kind of like a 150 ohm resistor to a preamp input stage. Mackie has learned that some of their customers try to verify their specs - they may not do it in the right way, but when they get different numbers than what are published (some confuse this with "promised"), they ask questions.

If you start to compare noise levels, you'll find that within a couple of dB they're all about the same (and well below any troublesome level). What you should be interested in is how much gain you have available (important if you use low-output mics or mic quiet instruments at a distance to get some ambience) and what happens when running at full gain.

For example, at full gain, the mic inputs on the VLZ Pro mixers roll off about -5 dB at 20 Hz. The Onyx preamp is considerably better, down only about 1 dB at 20 Hz.